This invention relates generally to thrusting devices and more particularly to simple, lightweight fluid operated thrusters.
Thrust devices that have been used in the past which are powered by either cold or hot gases generally are arranged that the thrust-time curve of the device follows the internal gas pressure of the device. This is especially true in the case of the basic cylinder and piston arrangement into which the gases are fed. The problem especially with hot gas devices, is that peak pressures are felt for only a very short period of time. Therefore, the devices being thrusted as well as the backup structure for the thruster must be of sufficient strength to accommodate a high load over a very short period of time. This in turn increases the weight of the parts which is highly undesirable in the case of aircraft, missile, or space structures.
Some thrusters are equipped with dual pistons of a telescopic nature wherein an inner piston rides in an outer piston which in turn rides a cylinder wall. With these types of thrusters, incoming gas at high pressure operates on the total areas of both pistons thereby pushing down both the outer and inner pistons simultaneously. Then, after the outer piston reaches bottom, the inner piston with the small area operating on low pressure gas continues on its stroke. It is highly desirable for the inner piston to complete its stroke first while pressures are high and are acting on the small piston area. Then, when the inner piston reaches bottom, the outer piston strokes using low pressure gas. To accomplish this, some thruster designs incorporate complex and heavy latching mechanism to keep the outer piston locked while the inner piston completes its stroke. In this fashion, a more even thrust versus time can be produced avoiding the high peak load and stretching out the maximum load over a longer period of time. This promotes efficiency in the thruster device creating high thrust over a long period of time with minimal peak forces.